Process fob developing fabrics



Aug. 10, '1937. H. AUBAUER 2,089,920

PROCESS FOR DEVELOPING FABRICS PRINTED WIT H VAT DYE STUFFS Filed July19, 1933 ank confaining wafer and heating elements A (heai/ng e/emenis)B\ (heafing e/emeni k G) K INVENTOR 5 '1 I L ATTORNEYS Patented Aug. 10, 193'! UNITED STATES raocuss roa nnmormo names ram'run wrrn varnrns'rurrs Hans Aubauer,

vlennmfiustrimassignortoGeny eral Aniline Works, Inc., New York, N. Y.,a corporation of Delaware Application July 19, 1933, Serial No. 681,194

In Germany itclaims.

The present invention relates to a process of developing fabrics printedwith vat-dyestufls.

I As is known, fabrics which have been printed with vat-dyestuil's andon whichthere are present 5 besides the dye-stuff and a thickening agentan alkali and hydrosulfite or a derivative thereof, are developed in adouble-walled steaming device in which the goods are subjected to theaction of steam at a temperature between about 100 C. and about 120 C.,with exclusion of air. In these rather complicated devices the dyestuflis reduced and the leuco compound is fixed on the.

goods at the same temperature. The fabric thus prepared is then furthertreated in order to cause oxidation of the leuco-compound.

I have found that the development of moist printed goods of the abovedescribed kind is simplified and at the same time better prints areobtained with a more advantageous utilization of the dyestufl, byeflecting the reduction of the vat-dyestufi on the moist goodsinstantaneously, that is to say, as rapidly as possiblevby means ofheat, advantageously at temperatures below 100 C., for instance at about70 C. to about 80 C., namely by exposing the goods in a moist atmosphereto a source of heat having a temperature exceeding that to which thegoods are to be heated and removing them from the influence of the saidsource as soon as they have attained the desired temperature, so thattheir temperature then falls and the leuco-vat-dyestuif is fixed on thefiber at a temperature below the temperature to which the goods wereheated for reduction. The exclusion of air during the reduction andfixation of the dyestufi is not necessary but advantageous in somecases.

The invention is based on the following observations:

It has been found that the reduction of practically all vat-dyestuffs tothe leuco-form by means of suitable hydrosulfite concentrations occursat about 70 C. to about 80 C. almost instantaneously, so that theapplication of higher temperatures and the prolongation of the time ofreduction to half a minute or more, as is customary with the knowndevices, is not necessary.

It has also been found that hydrosulfite decomposes the more easily thelonger it is exposed to heat and the higher the temperature, so that itis not advantageous to heat goods containing hydrosulfite for a longertime and to a higher temperature than is necessary. By developing in theknown steaming devices under the usual conditions under which thehydrosub June 11, 1933 I fite or its derivative is heated for about 2 toabout 5 minutes at about 100 C. to about 120 C., decomposition of thehydrosulflte generally occurs too quickly. It is true that also underthese unfavorable conditions the dyestufl is completely 5 transformedinto the leuco-form, but it is very important that the hydrosulfitewhich has been used in excess is not decomposed completely and that thenecessary excess of reducing agent is always present, in order that-thedyestufl may be 10 retained on the goods in its leuco-form until it isfinally fixed. By developing the goods in the known devices, theleuco-dyestufls, in spite of the exclusion of air, are often decomposed,probably owing to lack of a reducing agent, and there- 15 fore, cannotbe completely utilized. Only if the fixation process is so conductedthat the conditions which cause the hydrosulphite to decompose areadapted as much as possible to the fixation process, is an almostcomplete utilization of the dyestufl guaranteed.

Furthermore, it has been found that the leucovat dyestuifs are bestfixed on the goods at temperatures which are below those required forthe most rapid reduction of the dyestuffs; the members of the group ofdyestuffs which dye at a raised temperature are advantageously fixed atV a temperature between about 50 C. and about 60C. and those of thegroup of dyestuffs which dye in the cold are best fixed at roomtemperature.

The present process, in contradistinction to the processes hithertoknown, offers the possibility of observing the above described favorableconditions of reduction and fixation of the vat dyestufls and thusallows of obtaining the most favorable printing results.

The practically instantaneous heating of the moist goods, as is requiredaccording to the present invention, to the temperature which is the mostfavorable for the reduction of the dyestufi, for instance to about 70 C.to about 80 C., may be effected, for instance, by passing the moistgoods through a short distance over heating elements which can beregulated, for instance, electrlc heating plates or resistance heatingbodies with directed heat rays, the radiating thermal energy beingadjusted according to the quality of the goods (for instance, thick orthin fabrics) and their content of moistm'e.

The quantity of radiated heat may advantageously be regulated by meansof some known thermostatic device; thus, for instance-part of thecurrent to be regulated may be conducted over a contact which is in ascomplete a vacuum,

as practicable, the circuit being opened and goods are conducted at ashigh a speed aspossible over aroller R1 alongside and round a body Hwhich is heated to a suitable temperature and is contained in an opentank K, and then over. the roller R2 but so that the dyestufi on thegoods is completely reduced. The dyestuif is advantageously fixed on thegoods by a subsequent passage through the air, the temperature fallingrapidly to room temperature.

For other dyestuffs which are best' fixed at a about 50 C. to about.600., a device such as is diagrammatically shown in Fig. 2 may be used.The chamber K which may have the shape of a box or a drum or the likeand contains the heating element B is in this case so large that thegoods after having passed the heating element have to travel along apath W before leaving the 5 chamber K. Consequently, the temperaturedrop is not so rapid and the fixing may occur,for

instance, at a temperature of 50 C. to 60 C.

Since it is necessary for the development of the dyestuifs that thegoods should have a certain humidity and, on the other hand, a thinmaterial when heated easily loses its relatively small quantity ofhumidity, it is advantageous to combine the developing devices accordingto the present invention with a humidifier as diagrammatically shown inFig. 2. Such a humidifier may be constructed in a simple manner. forinstance by a heating element A which can be regulated and is placed inwater, which is thereby evaporated in the required quantity.

The humidifier may be controlled, for instance, on the principle of ahygrometer or by conducting the grid circuit of a tube electrode overtwo condenser plates which are placed in the chamber. According to theamount of humidity the dielectric constant varies and therefore also theresistance between the condenser plates. In this manner the humidifieralso may be controlled.

By such a control of the humidity the goods are provided with thequantity of humidity which is the most advantageous and the arrangementis distinguished from the known developing devices especially by. thefact that a deficiency or a detrimental excess of humidity is avoided.The steaming devices hitherto known have the drawback tl'iat thegoods,-in certain circumstances when introduced in a moist condition,take up a considerable quantity of condensation water which easilycauses the dyestufi to bleed.

As thickening agents for the printing pastes there may be used thoseusually applied. It is not to be fearedthat the prints will bleed on thefabric since the printed goods, after drying,

are passed only for, a very short time through.

the bath containing an alkali and a reducing agent and also during thereduction are exposed only for a very short time to the action of heat.The cellulose derivatives known as useful for the purpose in questionhave proved to be the most advantageous thickening agents.

The invention is applicable not only to goods which have been printedwith a dyestufi and a thickening agent, dried and thenpadded for a Ishort time in a'bath containing an alkali and a reducing agent, but alsoto goods which have been printed with a paste containing the dyestafi,

an alkali, a reducing agent and a thickening agent, dried and moistenedfor a short time.

Hydrosulfite may advantageously be used as reducing agent in the presentprocess; with a slight modification, however, the process is alsooperative if derivatives of hydrosulfite, such as formaldehydesulfoxylates are used. In this case it is only necessary to start with ahigher temperature of the heating device or to heat the goods at firstto a higher temperature, for instance to 100 C., until the sulfoxylatehas been decomposed and hydrosulfite has been formed,

whereupon the process may be carried through practically in the mannerdescribed for the use of hydrosulfite. Y

If dyestuffs are used which are known to fix best on the goods in thecold, it has been found to be "important to use the the optimum alkaliconcentration for-the fixing process; This is practically attained bypadding in a bath which' contains, as far as possible, 1 molecularproportion of hydrosulfite for about 2 molecular proportions of caustic.soda in solution so that, the hydrosulfite being nearly completelyconsumed,

the caustic soda solution is neutralized to the most favorable extent.

The following examples serve to illustrate the invention, but they arenot intended to limit it thereto,

(1) A paste is prepared from grams of a 25.8 per cent. paste of thecommercial dyestufi No. 1229 of Schultz, Farbstofftabellen 1931(N-dihydro-1.2.1.2-anthraquinoneazine) 200 grams of water,

60 grams of thiodiethyleneglycol and 665 grams of starch tragacanththickening (60 grams of tragacanth and grams of starch per liter).

This printing color is printed on a fabric of I travel through the boxand cool, by radiation or dissipation of heat, to about 65 C. The goodsthus treated are finished as usual (rinsed, oxidized, rinsed, soaped)There are obtained yivid blue patterns of good properties of fastness.

(2) An artificial silk fabric is printed with the following printingcolor:

200 grams Ofa 12 per cent; paste of the stufi obtainable bycarbazolation of -a-,a-. tr1- anthrimide (according to U. S. Patent No.

1,900,350) are made into a paste with 800 grams ofmethyl-cellulos-thickening' The goods thus printed are passed bath at 400. containing 50 cc. of caustic soda solution 01140? B. 50 grams ofhydrosulfite and 200 grams of Glaubers salt The well squeezed goodstravel through the apparatus described in Example 1 and are subsethrougha v, perliterjquently passed through the air whereby they are cooled toabout 40" C.

Thereupon, the goods are finished-as usual.

.150 grams Ma 20 per 'cent.-, paste of 9.4.8.9-di- I bath containing perliter:' 15

' bnzpyrene-5.10-quinone are made into a paste 850 grams ofmethylcellulose-thickening (1:10).

The printed goods arethen passed through a 100 grams of hydrosulflte 50cc. of caustic soda solution of 40 lzugrams of Glauber's salt.

The goods are squeezedto 100 per cent moisture and conducted for about10 seconds over a plate heated by steam which heats the goods in thetime specified to 70 C. 'Ihereupon. the goods are passed through the airfor-about 60 seconds and are rinsed, oxidized, rihsfedfand soaped. Thereare obtained vivid yeiiow-oi-aageprints.

(4) Linen fabric is printed with the followin printing color: v

150 grams of a 20. percent paste of the commercial' amend; its. 1260 ofschultz Ii'arbstoiftabellen' V 1931. (dimethot'y-dihydrodiben- W 1 (60mmof methylcellulose-starchethickening, (100 grains of methyl.celluios,e,-40 grams of starchv for 1 kilo, oi thickening) 90'grams of water;

the goods thus printed are padded with a solution prepared from. 100grams offormaldehydesulfoxylate 100grams of potassium 75 grams ofthiodiethylene glycol 50grams oi Glaubers salt.

3 grams of a wetting agent 6'12 grams of water and 100 per centhumidity. Thereupon,' the moist goods are introduced into the abovedescribed apparatus as shown in Figure 2 The goods then travel for afurther 2 minutes through the apparatus in which they are cooled byradiation or dissipation of heat of the box to about 60 C. to about 70C. The goods are then finished as mm. more are obtained vivid very fastgreen prints. p

The operations are as descflbed in. Example 1. There are used fabrics ofdifferent weight and different content of moisture, for instance, heavycloth, light voile. During the passageof these kinds of clothessentially different in weight and moisture, the moisture in the 11xingapparatus is controlled by means of a device that controls the humidity.-At the same time,

the temperature of the goods is regulated by an automatic electrictemperature-regulator.

(8) A mixed cotton viscose fabric is printed with the following printingcolor:

200 grams of a 23 per cent paste of the commercial dyestuff No. 1265 ofSchultz, Farbstofltabellen 1931 (dichioro-isoviolanthrone),

500 grams of starch-tragacanth (40 grams of tragacanth, 80 grams ofstarch per kilo of printing paste) are made into a paste with 120 gramsof potassium carbonate 100 grams of formaldehyde-sulfoxylate 80 grams ofglycerine.

The goods thus printed are conducted through the apparatus referred toin Example 4, whichcontains also the humidifier described above.

, The humidifier imparts to the goods the necesand hydrosulflte or aderivative thereof, are dried and only immediately before they areintroduced into the box, are moistened with water by padding themaccording to one of the usual methods.

I claim: 3 1. A process of developing moist fabrics which have beenprinted with' vat-dyestuffs and on which there are'present, besides thedyestufl and a thickening agent, an alkali and a reducing agent of thegroup consisting of hydrosulflte and the formaldehyde derivativethereof. wherein for reducing the dyestufl the goods are heated rapidlyto a temperature below 100 C. by exposing them in a moist atmosphere toa locally limited source of heat, removing them from the influence ofthe said source of heat as soon as the dyestufl is reduced and fixingthe dyestufl' in 2. A process of developing moist fabrics which havebeen printed with vat-dyestufls. and on which there are present. besidesthe dyestufl. and a thickening agent, an alkali and a reducing agent ofthe group consisting of hydrosulflte and the formaldehyde derivativethereof, wherein for reducing the dyestufl the goods are heated rapidlyto a temperature of about 70 C. to about 80 by exposing them in a moistatmosphere to a locally limitedsourceof heat, removing them from theinfluence of the said source of heat as soon as the dyestuif is reducedand fixing the dyestufl in the reduced state on the fiber at atemperature lower than that to which the goods were heated forreduction.

HANS 'AUBAUER.

